Thaumastocoris peregrinus (Bronze bug) is a sap-sucking pest (Order Hemiptera: Thaumastocoridae) exclusively found on eucalyptus trees. Bronze bug infestations have occurred in the Southern hemisphere and pose a threat to commercial eucalyptus farming in Australia, Africa, and South America. Infestations have been observed, for example, in the species E. camaldulensis, E. tereticornis and E. smithii and the hybrids E. grandis×E. camaldulensis and E. grandis×E. urophylla. Bronze bug infestation reduces the photosynthetic ability of the tree, resulting in stunted growth. Severe infestation may cause death of trees. Efforts to control Bronze bug infection of eucalyptus have included attempts to isolate naturally resistant plants and natural predators. Such efforts, however, have met with limited or no success.
Certain characteristics of Bronze bug infestations lead to difficulties in controlling infestations with chemical pesticides. Bronze bug infestations tend to spread rapidly. Control of infestation would thus necessitate repeated spraying. Bronze bug, moreover, tend to aggregate in the mid-canopy, which is difficult to penetrate with insecticides. Even if feasible, chemical pesticide control has disadvantages. Chemical pesticides are potentially detrimental to the environment, are not selective and are potentially harmful to non-target crops and fauna. Chemical pesticides persist in the environment and generally are metabolized slowly, or not at all. Chemical pesticides accumulate in the food chain, particularly in the higher predator species where they can act as mutagens and/or carcinogens to cause irreversible and deleterious genetic modifications. Crop pests, moreover, may develop resistance against chemical insecticides because of repetitive usage of the same insecticide or of insecticides having the same mode of action.
RNA interference or “RNAi” is a process of sequence-specific down-regulation of gene expression (also referred to as “gene silencing” or “RNA-mediated gene silencing”) initiated by double-stranded RNA (dsRNA) that is complementary in sequence to a region of the target gene to be down-regulated. Down-regulation of target genes in multicellular organisms by means of RNA interference (RNAi) has become a well-established technique. U.S. patent application publications US 2009/0285784 A1 and US 2009/0298787 relate to dsRNA as an insect control agent and are hereby incorporated herein by reference in their respective entireties. U.S. Pat. No. 6,506,559, U.S. patent application publication 2003/00150017 A1, International Publications WO 00/01846, WO 01/37654, WO 2005/019408, WO 2005/049841, WO 05/047300 relate to the use of RNAi to protect plants against insects. International application, PCT/US12/31423, filed Mar. 30, 2012, relates to RNA-mediated control of eucalyptus pests in the Gall Wasp family. Each of the foregoing patents and published applications is hereby incorporated by reference in its entirety.